Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

30. Peptides and Proteins

Disulfide Bonds

Organic Chemistry

30. Peptides and Proteins

Disulfide Bonds

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Multiple Choice

Determine which of the following peptide chains could be further stabilized by intramolecular a disulfide bridge(s).

Trp–Cys–Met–Ile–Val–Gln–Arg–Ala–Arg–Gly–Glu–Met–Pro–Leu–Phe

Ala–Phe–Met–Ser–Trp–Ser–Leu–His–Arg–Arg–Ala–Pro–Thr–His–Val

Gly–Leu–Ala–Glu–Gln–Cys–Ser–Met–Gln–Leu–Asn–Cys–Trp–Ile–Val–Ala

Phe–Ile–Leu–Cys–His–Arg–Tyr–Thr–Phe–Met–Arg–Ala–Asn–Ile–Phe–Lys

Gly–Asn–Val–Val–Ille–His–Leu–Thr–Pro–Met–Tyr–Ser–Cys–Trp–Leu–Ala

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Verified step by step guidance

Identify the amino acid cysteine (Cys) in each peptide chain, as it is responsible for forming disulfide bridges.

Examine each peptide chain to determine if there are at least two cysteine residues present, as a disulfide bridge requires two cysteine molecules to form a bond.

For the first peptide chain, Trp–Cys–Met–Ile–Val–Gln–Arg–Ala–Arg–Gly–Glu–Met–Pro–Leu–Phe, note that there is only one cysteine residue, so it cannot form a disulfide bridge.

For the second peptide chain, Ala–Phe–Met–Ser–Trp–Ser–Leu–His–Arg–Arg–Ala–Pro–Thr–His–Val, observe that there are no cysteine residues, so it cannot form a disulfide bridge.

For the third peptide chain, Gly–Leu–Ala–Glu–Gln–Cys–Ser–Met–Gln–Leu–Asn–Cys–Trp–Ile–Val–Ala, identify two cysteine residues, which means it can form a disulfide bridge, thus stabilizing the peptide chain.